The Prader-Willi syndrome (PWS) represents an ideal model in which to study various common clinical problems such as obesity, obsessive-compulsiveness, hypotonia, and mental retardation. The genetic location of this neurobehavioral syndrome has been narrowed to a 2 MB region on chromosome 15q11-q13. In addition, PWS together with the Angelman syndrome (AS) represent the best examples of genomic imprinting in humans. Disruption of the normal imprinting process has been shown to be involved in the etiology of a number of birth defects, genetic diseases, and cancers. The International Prader-Willi Syndrome Organization (IPWSO) was founded in 1991. The fourth triennial conference will be held in St. Paul, Minnesota in June 2001. It will be comprised of separate Scientific, Provider, and Parent Conferences. The Scientific Conference will run from June 27-29, 2001. Separate scientific sessions will include Genetics, Growth Hormone, Obesity and Metabolism, Endocrinology, Psychology and Psychiatry, Animal Models, and Medical and Dental Issues. For each session there will be one to two invited "State of the Art" speakers, as well as speakers selected from solicited abstracts. The expected audience will range from established investigators in the clinical and basic sciences to young investigators embarking on new research careers. This application will provide travel stipends for the young investigators (i.e., graduate and medical students, residents, postdoctoral fellows, and beginning faculty) to present their research. Private industry support will be sought to provide travel for the "State of the Art" speakers.